Determination of <sup>13</sup>C/<sup>12</sup>C ratios of urinary epitestosterone and its main metabolites 5α‐ and 5β‐androstane‐3α, 17α‐diol
Bibliographic record
Abstract
Epitestosterone (17alpha-hydroxy-androst-4-en-3-one, EpiT) belongs to the list of prohibited substances of the World Anti-Doping Agency (WADA). Although it possesses no anabolic effect, it is presumed to be misused by athletes in order to mask administration of testosterone (T) by lowering the urinary T/EpiT ratio.To improve detection, an excretion study with 40 mg of orally administered EpiT was conducted focusing on the metabolites of EpiT: 5alpha- and 5beta-androstane-3alpha,17 alpha-diol (5aEpiD and 5bEpiD). A reference population of n = 74 volunteers was investigated to elucidate the urinary concentrations of these steroids.In order to prove whether an unusual finding in urinary concentrations or ratios is due to an illicit intake of steroids or due to physiological elevation, determination of carbon isotope ratios is advisable. A method for isotope ratio determination was developed to enable (13)C/(12)C ratios of EpiT, 5bEpiD, 5aEpiD, pregnanediol and androsterone and etiocholanolone to be measured from a single urine specimen. The method's validity was tested by applying linear mixing models and specificity was ensured by means of gas chromatography/mass spectrometry analysis. delta(13)C values at natural levels were determined with a reference population and both Delta values and corresponding reference limits were calculated.Considering the implemented EpiT-metabolites, a more than twofold extension of the detection time of EpiT administration was achieved with both the urinary concentration thresholds and the (13)C/(12)C ratios.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".